1. Field of the Invention
The present invention relates to a data replication method and system in a Database Management System (DBMS).
2. Discussion of the Background
Database replication is a technique for copying an object stored in a single database to another database physically separated to thereby be used in at least two database servers in a distributed database scheme. This replication technique may distribute accesses of application programs using the same object to various database servers, thereby increasing the performance or allowing a replicated database server to have other applications, and thus simultaneously satisfying different operation requirements. Also, the replicated database may be rapidly replaced when faults occur in a database server during the operation, thereby significantly increasing reliability.
The above-described replication technique may be utilized when a single database server fails to satisfy requirements for the performance of the application programs. For example, read operations are distributed to various database servers with identical data, thereby improving the performance of the entire system.
FIG. 1 is an example used for describing a structure of a replication system for load distribution according to a conventional art. In the case of general replication, a master database 102 may allow read and write operations, however, a slave database 103, 104, or 105 may allow only the read operation, and thereby performance-improvement effects using the data replication may have limitations for write operations, and show dramatic improvements for read operations. Thus, many applications such as a blog, bulletin board, news, and the like which are used for Internet services and the like may be included in the above general replication. Specifically, data in a web service 101 may be stored in a master database 102 through a write operation, and modifications of the master database 102 may be reflected in slave databases 103 to 105 using the replication technique. Also, data may be provided through the read operation. In this instance, the data may be provided via the slave databases 103 to 105 in view of characteristics of the web services 101 having a significantly high frequency of occurrence of read operations as opposed to write operations. As described above, when using the replication technique, an aggregate load in the database may be distributed, and any one of slave hosts may replace a master host when a fault occurs in the master host including a master database, thereby increasing reliability.
However, as for the replication technique of the conventional art, there arise several problems in that change of a schema may not be replicated in the slave database, change detail-automatic extraction via the slave database may be impossible, and a desired replication environment such as a ratio of the master host to the slave host of N:M may be difficult to be achieved. Also, disadvantageously, an object to be replicated may be designated only in a database unit, a replication delay time may be difficult to be measured, and data synchronization status between the original and the replication may be difficult to be confirmed. Also, disadvantageously, a master transaction archival log may not be confidently eliminated by checking the replication processing status.